What kind of Documentation a game needs?

So im very used to write extensive documentation on software development, like Class Diagrams, Use Case Diagrams and others (interaction, sequences, etc etc) and since im very interested on launching a game im developing this year i was wondering what Documentation other people use for games?

I think just Use Case diagrams because since Unity its component based, its kind of useless a Class Diagram.

Thanks!

Depends how extensive your codebase is. If its a relatively simple game you could use use cases, the farther you get into development the more you might be extending the native Unity classes and needing more extensive planning. We use index cards to great effect. Its very handy to draw out something that explains mechanics, to script out sequences, etc before you try to build it though.